Java has been a source of frustration for many of us trying to use the USPTO's private PAIR.
If you don't use the website for a two week period, Apple's MAC OSX now disables JAVA. I find myself having to go to the Java Web Site to test for JAVA install in order to reactivate it. A block pop up window still pops up every time I use it but you can dismiss it. You are probably not seeing the block pop up window because JAVA was automatically disabled. Be sure to use the Java web site often to be sure the proper version is installed and functioning. Good Luck.